The present invention relates generally to a communication network used to maintain communication exchanges within an enclosed premises; and, more particularly, it relates to a method and apparatus for maintaining communication exchanges utilizing both infrared and radio frequency transmissions in a premises such as an office building, hospital, factory floor, or the like.
As is well known, radio frequency (RF) transmissions have been used to maintain point to point communication. However, use of RF transmissions in a premises can cause several problems. For example, RF transmissions can interfere with the proper functioning of other equipment in the premises. Such interference is particularly undesirable in a premises such as a hospital, where the equipment may provide life support to patients. Further, because the Federal Communication Commission (FCC) has allocated only certain frequencies to premises RF communication networks, interference may also occur between adjacent premises. Thus, RF communication in a premises may be hindered by RF noise from surrounding premises. Such noise may become a significant burden to communication in a premises located in a crowded, city environment.
These interference problems may also be enhanced given the physical layout of most premises. Specifically, a typical premises comprises structural supports and walls which limit the penetration of RF transmission. If the transmission power is too low, certain areas may arise wherein RF transmissions cannot be received (i.e., "dead zones"). While increasing the RF transmission power may increase penetration and eliminate dead zones, it also increases the likelihood that the above-described interference problems may occur.
In addition, increasing the RF transmission power may also be undesirable for health reasons. Specifically, it has been alleged that RF transmissions may potentially cause damage to human tissue or cells, and thus may be carcinogenic. As a result, it may be desirable to not only limit the RF transmission power in a premises, but also limit the use of RF transmissions altogether.
As is also well known, modulated infrared light has also been used to maintain point to point communication. Use of infrared light as such in a premises is a desirable alternative to RF transmissions because infrared light is rather harmless to humans and does not cause the interference problems discussed above. However, use of infrared light for communication in a premises causes a unique set of problems. For example, infrared communication is limited in range because it is directional, i.e., it requires "line of sight" type transmissions. As a result, it is difficult to provide communication over an entire premises using only infrared transmissions. In addition, dead zones are created easily in infrared systems by mere interruption of the light stream, resulting in a loss of data.
While infrared systems are less expensive than those using RF, they are not a viable alternative to RF because of these problems. Infrared communication has had virtually no market use in mobile environments, and has only been a solution to replacing RS232 and parallel wiring in short distance, line of sight environments such as between a personal computer and associated input and output devices (e.g., keyboard, mouse, printer, etc.).
In airplanes, the use of electronic equipment is permitted but with many restrictions. For example, during take off and landing, all such equipment must be turned off to prevent unintentional yet often inherent RF transmissions from interfering with cockpit electronics. Such interference proves annoying yet is tolerated by cockpit crews during the less critical period between take off and landing. Moreover, at all times during flight, airlines prohibit passengers from using intentional, RF transmissions within an airplane.
As a result, while in flight, passenger are virtually cut-off from their normally available communication and data channels outside of the airplane. Similarly, two or more passengers on the same flight are prevented from wirelessly networking unless their electronic equipment is either within line of sight of the other's equipment (for infrared communications) or within very close proximity (for a wired linkup). However, many types of wired communication links are designed with maximum bandwidth for rapidly exchanging data. Higher bandwidth, usually results in higher emission levels of unintentional RF energy. Thus, such wired links are not desirable within airplanes.
Because such line of sight and proximity conditions cannot be guaranteed, networking involving a plurality of passengers within airplanes rarely proves viable. With little or no means of communicating, passengers are often unproductive, bored and/or anxious.
Also during flight, through monthly magazine publications, airlines offer duty free or other items for sale, provide information regarding in-flight services and provide route and terminal information. Flight attendants are burdened with assisting passengers in finding, understanding and supplementing such information. The attendants must also assist passengers by taking orders for the items being purchased. Because flight attendants are busy with many other tasks, passengers often forego purchasing and requesting information while in flight.
Airlines also desire to provide further booking or travel agency services to passengers while in-flight. Such services are accessible via telephones within the airplanes, but, because of the limited voice interface, utilization has not meet expectations.
Hence, it would be highly desirable to solve the foregoing variety of enumerated problems while maintaining reliable communication exchanges between a plurality of devices operating within an enclosed premises. It is therefore an object of the present invention to provide a method and apparatus which minimizes the need for RF communication while at the same time maximizes the benefits obtained from infrared communication.
It is another object of the present invention to provide a method and apparatus for maintaining communication in a mobile environment using both infrared and RF transmissions.
Another object of the present invention is to provide a method and apparatus for permitting airplane passengers to maintain communication connectivity during flight to local and remote information and services, other passengers and remote associates, without interfering with cockpit equipment.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention and claims with reference to the accompanying drawings.